The Commonwealth was the republican government which ruled first England and then the whole of Britain and Ireland during 1649 - 1653 and 1659 - 1660. The term is also loosely used to describe the system of government during the whole of 1649 - 1660, the years of the Interregnum[?], although during 1653 - 1659, the government is properly called The Protectorate and took the form of direct personal rule by Oliver Cromwell, the Lord Protector.
... or adjective, Royalist, can have several shades of meaning. At its simplest, it refers to an adherent of a monarch or royal family.
Of the more specific uses of th ...